Glucocorticoids are responsible for several physiological functions including answer to stress, immune and inflammatory responses as well as stimulation of hepatic gluconeogenesis and glucose utilization at the periphery. Glucocorticoids act via an intracellular glucocorticoid receptor (GR) belonging to the family of the nuclear steroidal receptors. The non-activated GR is located in the cellular cytoplasm and is associated with several chaperone proteins. When a ligand activates the receptor, the complex is translocated in the cell nucleus and interacts with the glucocorticoid response element which is located in several gene promoters. The receptor could act in the cell nucleus as an homodimer or an heterodimer. Moreover several associated co-activators or co-repressors could also interact with the complex. This large range of possible combinations leads to several GR conformations and several possible physiological answers.
Pathologies like diabetes, Cushing's syndrome or depression have been associated with moderate to severe hypercortisolism (Chiodini et al, Eur. J. Endocrinol. 2005, Vol. 153, pp 837-844; Young, Stress 2004, Vol. 7 (4), pp 205-208). GR antagonist administration has been proven to be clinically active in depression (Flores et al, Neuropsychopharmacology 2006, Vol. 31, pp 628-636) or in Cushing's syndrome (Chu et al, J. Clin. Endocrinol. Metab. 2001, Vol. 86, pp 3568-3573). These clinical evidences illustrate the potential clinical value of a potent and selective GR antagonist in many indications like diabetes, dyslipidemia, obesity, hypertension, cardiovascular diseases or depression (Von Geldern et al, J. Med. Chem. 2004, Vol 47 (17), pp 4213-4230; Hu et al, Drug Develop. Res. 2006, Vol. 67, pp 871-883; Andrews, Handbook of the stress and the brain 2005, Vol. 15, pp 437-450). This approach might also improve peripheral insulin sensitivity (Zinker et al, Meta. Clin. Exp. 2007, Vol. 57, pp 380-387) and protect pancreatic beta cells (Delauney et al, J. Clin. Invest. 1997, Vol. (100, pp 2094-2098).
Diabetic patients have an increased level of fasting blood glucose which has been correlated in clinic with an impaired control of gluconeogenesis (DeFronzo, Med. Clin. N. Am. 2004, Vol. 88 pp 787-835). The hepatic gluconeogenesis process is under the control of glucocorticoids. Clinical administration of a non-specific GR antagonist (RU486/mifepristone) leads acutely to a decrease of fasting plasma glucose in normal volunteers (Garrel et al, J. Clin. Endocrinol. Metab. 1995, Vol. 80 (2), pp 379-385) and chronically to a decrease of plasmatic HbA1c in Cushing's patients (Nieman et al, J. Clin. Endocrinol. Metab. 1985, Vol. 61 (3), pp 536-540). Moreover, this drug given to leptin deficient animals normalizes fasting plasma glucose (ob/ob mice, Gettys et al, Int. J. Obes. 1997, Vol. 21, pp 865-873) as well as the activity of gluconeogenic enzymes (db/db mice, Friedman et al, J. Biol. Chem. 1997, Vol. 272 (50) pp 31475-31481). Liver-specific knockout mice have been produced and these animals display a moderate hypoglycemia when they are fasted for 48 h excluding the risk of severe hypoglycemia (Opherk et al, Mol. Endocrinol. 2004, Vol. 18 (6), pp 1346-1353).
Mifepristone is also known to stimulate the Hypothalamus-Pituitary gland-Adrenal gland (HPA) axis via the activation of a feed-back mechanism which leads to an increase of endogenous corticosteroids circulating in the blood (Gaillard et al, Pro. Natl. Acad. Sci. 1984, Vol. 81, pp 3879-3882). Mifepristone also induces some adrenal insufficiency symptoms after long term treatment (up to 1 year, for review see: Sitruk-Ware et al, 2003, Contraception, Vol. 68, pp 409-420).
For GR modulators to be used in indications such as diabetes, dyslipidemia, obesity, hypertension and cardiovascular diseases it is necessary to limit the risk to activate or inhibit the HPA axis. Several strategies can be used to achieve this goal like to have a drug with a moderate to high liver selectivity or to get a drug which would not penetrate brain. Liver selectivity can be obtained by introducing liver targeting vectors in the molecule or by limiting the volume of distribution of the substance in the body. On the opposite for GR modulators to be used in indications such as adrenal/HPA imbalance, insomnia or depression it will be necessary to obtain a drug with a moderate to high brain selectivity.